An earth-boring drill bit can be mounted on the lower end of a drill string and rotated by rotating the drill string at the surface, actuation of downhole motors or turbines, or both. With weight applied to the drill string, the rotating drill bit engages the earthen formation and proceeds to form a wellbore along a predetermined path toward a target zone. The wellbore thus created will have a diameter generally equal to the diameter or “gage” of the drill bit.
An earth-boring bit in common use today includes one or more rotatable cutters that perform a cutting function due to the rolling movement of cutting elements of the cutters acting against the formation material. The cutters roll and slide upon the bottom of the wellbore as the bit is rotated, the cutting elements thereby engaging and disintegrating the formation material in its path. The rotatable cutters may be generally conical in shape and are therefore sometimes referred to as roller cones or roller cone cutters. The wellbore is formed as the action of the cones remove chips of formation material that are carried upward and out of the wellbore by drilling fluid that is pumped downwardly through the drill pipe and out of the bit.
The earth disintegrating action of the roller cones is enhanced by providing a plurality of cutting elements on the cutters. Cutting elements may include teeth integrally formed with the cone, or inserts attached to the cone. In each instance, the cutting elements on the rotating cutters break up the formation to form the new wellbore by a combination of gouging and scraping or chipping and crushing.